The people who choose to get close to deadly weather have "a wide variety of motivations," Wurman says.

There are those who are in it for "the thrill seeking," much like others who enjoy white water rafting or bungee jumping.

Others may hope to sell videos or photos.

There are those who both enjoy the chase and are fascinated by the science.

And there are those, like the researchers Wurman works with, who have specific missions and are there to study "how tornadoes form, why some tornadoes become strong and some don't" and hope to collect data that will make the storms easier to predict.

That said, "there's really no data set which is worth being injured for or dying for," Wurman says. "Our goal is to help reduce injuries or reduce deaths, not to get injured or die ourselves."

Wurman doesn't know why his friend Samaras and the other two men got caught by the tornado on Friday. Wurman's team had dropped data-collecting equipment in what they thought would be the path of the storm. Then, as they could see on mobile Doppler radar equipment, a second tornado was forming to the south of the main twister. That's when they decided to move east and out of the area.

It's possible, he says, that Samaras didn't realize there was a second tornado in the area. Or, that his escape route was blocked by traffic or something else.

"The storm chasing community and the research community is still absorbing the loss of Tim Samaras, his son and his colleague," Wurman says.

Wurman's team and other groups, he's sure, are evaluating their procedures "and whether or not what we're doing is safe."

But as for the reason why to do such work and whether it's worth it, Wurman says simply that: "If we can make the forecasts better, then fewer people will die."

More from the conversation with Wurman is scheduled to be on Tuesday's Morning Edition. We'll add the as-aired version of the interview to the top of this post after it airs. Click here to find an NPR station that broadcasts or streams the show.

Oklahoma officials now say that 18 people died in last week's storms and floods. Three of them were tornado researchers, professional storm chasers, who appeared on a Discovery Channel reality show on the subject.

Josh Wurman heads the Center for Severe Weather Research. We first heard from him on this program after the massive tornado that hit Moore, Oklahoma last month. He also appears in that Discovery Channel show and, as it happens, he too was chasing the deadly storm near El Reno that took his colleagues' lives. But Wurman decided to turn back. We called him to find out why.

JOSH WURMAN: We saw a couple of things that made us think we needed to get out of there for safety, one was that the storm was becoming completely wrapped in rain. So the tornado was impossible to see visually. And also, there was a second tornado spinning in the opposite direction about three miles to the south of the first tornado. So we found ourselves between two different tornadoes, and the situation was becoming unpredictable enough that I thought my team was at too much risk.

We took the data we had and we basically retreated east to try to regroup and intercept the storm closer to Oklahoma City.

WERTHEIMER: Well, now reading about that storm and about the deaths of your colleagues, I think anyone would wonder why take such terrible risks. Is there that much value in doing it, that much scientific value?

WURMAN: Storm chasers have a wide variety of motivations. And many storm chasers, of course, are thrill-seeking. Scientists like myself, we're really not getting much thrill out of it. We have very particular missions. They're aimed at answering important questions about tornado science. And these questions are aimed at enabling forecasts to get better. People die in tornados, and if we can make the forecast better, then fewer people will die.

WERTHEIMER: Do you have any idea why your colleagues did not make the decision that you made, to try to get out of its way?

WURMAN: Tim Samaras is known as a very responsible, very experienced, very skilled storm chaser. And I'm surprised. He would be one of the last people I would expect to have been caught up in a storm like this, because he knew when to be cautious. We don't know the details of exactly what happened. So we don't know if it was related to a decision or something that was really truly unpredictable.

WERTHEIMER: What does this do to the community of storm chasers to have a crew like Mr. Samaras' lost in a storm?

WURMAN: I think the storm-chasing community and the research community is still absorbing the loss of Tim Samaras, his son and his colleague; trying to really understand whether this reflects on our techniques - on whether or not this activity, the way it's been done in the last few years, the way it's evolving - can continue to be safe.

My team, we've never had an injury. We've never had a vehicle destroyed. But still, my team is going to be meeting and reevaluating its procedures. There's really no data set which is worth being injured for or dying for.

WERTHEIMER: Mr. Wurman, thank you very much.

WURMAN: Good talking to you.

WERTHEIMER: Josh Wurman of the Center for Severe Weather Research in Boulder, Colorado.